1. Field of the Invention
The present invention relates generally to the construction and use of medical instruments for retrieving deleterious materials from body lumens. More particularly, the present invention relates to a catheter having a slack capture net at its distal end and means at its proximal end for opening and closing the net to capture and retrieve materials from body lumens.
The retrieval of ureteral stones remains a challenge and an occasional frustration to the treating surgeon. While blind retrieval techniques have been replaced by methods which employ direct visualization using a variety of endoscopes, stone retrieval can still be troublesome because of inadequacies in the retrieval device employed.
Conventional ureteral stone retrieval devices fall into several categories, including baskets, pincer-like forceps, graspers, and slings. Basket retrieval devices generally employ collapsible wire prong structures having relatively large openings which allow passage of small stones and stone fragments. The capture of large stones can also be difficult since the stone will frequently hinder movement of the basket in order to engage the stone. Such baskets also have a tendency to lose the stones as the basket is being withdrawn from the ureter.
The use of pincer-like forceps, graspers, and slings, is similarly problematic. Such devices usually can capture only one stone at a time. Frequently, vision through the ureteroscope is sufficiently poor to render capture of single stones difficult.
For the reasons, it would be desirable to provide improved devices and methods for capturing ureteral stones during stone removal procedures. It would be particularly desirable if the device could be used for other medical procedures, including the removal of biliary stones from the biliary tract, the removal of atheroma and plaque from the vascular system, and the like.
2. Description of the Background Art
U.S. Pat. No. 4,706,671, describes an atheroma removal catheter having an expandable helical coil at its distal end. U.S. Pat. No. 4,650,466, describes an angioplasty catheter having an expandable woven tube and optional internal filter for collecting plaque dislodged from a blood vessel by the tube. U.S. Pat. No. 4,873,978, describes an expandable strainer which may be introduced downstream of an angioplasty procedure to capture released emboli. U.S. Pat. 4,030,503, describes an embolectomy catheter having a helical wire structure at its distal end.